The cab of the vehicle needs to be tilted about a transverse axis from a normal operating position to a forward position so that the engine is exposed to facilitate servicing. Many tilting mechanisms for making a vehicle cab tilt are well known in the art. These mechanisms comprises of hydraulic system (hand actuated or electric motor actuated) or electric motor and gear mechanism or torsion bar mechanism.
However, the hydraulic mechanism is currently the most pervasive of all the other mechanisms. But some economy trucks have cabs which have to be tilted by hand without any intervening mechanism to reduce effort.
U.S. Pat. No. 4,222,451 discloses tilting cab for vans having a unitary interior volume containing a cab compartment and a rear compartment for cargo or passengers and an engine compartment extending substantially into the cab compartment. The forward tilting cab is attached to an engine compartment cover, which is raised to expose the engine of the van when the cab is tilted forward, thereby providing easy access to the engine to facilitate repairs and servicing of the engine.
The drawback of this invention is that an average sized person has to put one foot in stirrup and grasp handle with one or both hands, has to put all of his body weight to stirrup, lean backward and pull forward an handle causing cab to be tilted forward.
UK patent no. GB 2113619 describes a tilting mechanism for the cabs of vehicles. The mechanism comprises a cross member for attachment to the chassis of the vehicle, two hinge elements carried by the cross member and two lever arms hinged to the hinge elements for connection to the underside of the vehicle cab. The arrangement is intended for use in the conversion of fixed to tiltable cabs.
In this invention a jack is provided, one end of which is pivoted to the cross member of a chassis and other end is pivoted to the bottom of the cab at a position spaced from the hinge axis whereby controlled tilting of the cab can be achieved. The drawback of this invention is that it provides an inconvenient operating position, requiring the operator to be in front of the cab when it is tilting towards him.
Moreover the pivoted joints, at the top and bottom of the jack, force the jack also to rotate about the bottom pivot axis when the cab is being tilted. This makes the tilting operation inconvenient, especially when the tilting angle is large. This mechanism provides a stiff member at the bottom of the cab which hinders the cab movement on its suspension system thus affecting ride quality.
Patent Nos. 2002/0104699, WO 0125074, EP 1218235 and NL 1013228 discloses an invention related to a tilting mechanism for making the cab of a vehicle tilt relative to the chassis of the vehicle. The tilting mechanism comprises at least one fixing part that during the fitting of the cab on the chassis goes into a permanent engagement with a fixing part fitted on the cab and/or the chassis.
UK patent no. GB 1366220, France patent no. FR 2163056, German patent No. DE 2158484 and Sweden patent no. SE 378391 disclose tilting vehicle cabs in which the rear of a vehicle cab, which is mounted for tilting about a forward transverse axis, is supported on the chassis by adjustable and lockable piston/cylinder spring legs which engage the cab by sound insulating blocks. Cylinder is mounted by rubber rings in a collar on a chassis bracket, and block is adjustably screwed on the piston-rod. Cup, which seats block, is mounted on the cab and carries the spring leg locking mechanism, which includes a movable forked slide having an inclined end section. Slide, which is movable by means of a toothed segment lever, engages under the flange of a sleeve, which is slidably mounted on piston-rod and is urged downwardly by springs. As shown the spring leg is locked; on moving the slide to the left it disengages the sleeve and flange. A cab-mounted guide and a roller a bracket ensure lateral guidance of the cab. A cab-mounted spring biased catch and an extension of bracket insure against accidental tipping of the cab.
Patent Nos. WO 2007061371 and SE 529016 discloses cab tilt device fitted to a cab of a motor vehicle, e.g. a truck, comprising at least one cab tilt means adapted to applying to the cab a tilt force in order to tilt said cab in the forward direction of the cab about a chassis fastening arranged close to the cab's forward lower portion and comprising a spring means fastened pivotably close to the cab's forward lower portion, whereby a forward link means is adapted to being connected pivotably to the cab, and whereby a connecting means is connected to the cab, which connecting means is adapted to connecting said cab tilt means and said forward link means, whereby tilt force applied from the cab tilt means during tilting is adapted to being transmitted via the connecting means to the cab in such a way that the spring means is kept substantially compressed at least during initial stage of the tilting process.